This study is directed primarily toward developing new cell culture systems and utilizing existing differentiated cell types to study the relationship between in vivo and in vitro cellular aging. This program is organized into five projects. The first project is devoted to developing human epithelial and endothelial cell cultures that retain differentiated function in culture. Once the cell culture conditions have been refined to that these cells can be useful for cellular aging studies, we will investigate the effects of in vivo and in vitro aging on various differentiated functions that are relevant to the normal in vivo aging processes. The other four projects are devoted to studying the growth, nutrition and function of bovine endothelial cells and the dynamic changes that occur in connective tissue during in vitro and in vivo aging. In the second project bovine endothelial cells will be used to examine the fate of a number of endothelial cell specific functions as the cells age in culture. The third project will be involved in a detailed study of collagen biosynthesis and metabolism as a function of in vivo and in vitro aging in mouse and human corneal epithelium, endothelium and stroma, skin fibroblasts from individual animals of different ages. In the fourth project the precise nutritional requirements of bovine endothelial cells will be determined and the effect of key nutritional components on the growth and function of the cells at different points in their in vitro lifespan determined. The final project will investigate the relationship between proliferative and functional capacity and clonal heterogenity in cultures whose in vitro proliferative potential has been increased by treatment with fibroblast growth factor.